There is often a need to scribe lines from the edge of a piece of lumber or sheet material at a predetermined angle. For example, in framing a roof, the roof rafters must have their ends trimmed so as to establish the pitch angle of the roof to be constructed.
U.S. Pat. No. 4,138,914 issued on Feb. 13, 1979 for a “Saw Guide Apparatus” shows an adjustable saw guide useful for such purpose.
It is sometimes necessary to match an angle existing between two members in order to scribe the same angle on a workpiece. In such cases, any device used for this purpose must be able to be insertable between the members to be adjusted in conformity with the angle existing between these members.
Such guides and adjustable angles are often used for scribing lines on sheet material such as plywood, glass, drywall, etc. preparatory to cutting the same at a predetermined angle between the side edge of the sheet material.
U.S. Pat. No. 4,955,141 issued on Sep. 11, 1990 for “An Adjustable Pivot Angle Square Invention” describes such a general purpose adjustable angle device in which two elongated members are pivotally mounted to each other at one end and with a connecting member pivotally connected at one end to one of the members and sliding within an elongated slot formed in the other member. As the connecting member moves along the slot, varying adjustable angles are formed between the first two pivotally connected members.
See also U.S. Pat. No. 1,906,988 issued on May 2, 1933 for a “Measuring Apparatus” similarly showing a slotted member pinned at one end to a second elongated member with a connecting member pinned to the second member, and having one end attached to a slider moving through the slot. This enables a setting of an angle between the first and second mentioned members.
When such devices are used as a saw guide, a base member must be held against the lumber piece or other material being cut as the saw is advanced across the angled member with the base member being held in an accurately determined positioned as the sawing operation is continued. Oftentimes there is some slight shifting movement resulting from the urging of the saw edge against the member used as the guide, with a resultant loss of accuracy in the cut.
Various digital angle finders are currently available for measuring the tilt or inclination of an object or a work surface. Inclinometer-type angle finders typically feature a generally rectilinear configuration. A digital display screen and operating buttons are mounted on a vertical front face of the device. At least one side surface of the inclinometer functions as a reference surface for engaging the work surface or object to be measured for inclination.
The foregoing angle finders usually exhibit one or more shortcomings. The viewing screen is invariably oriented perpendicular to the ground and can be difficult to view and read clearly from above and/or peripherally. By the same token, positioning the push buttons that operate the finder (for example the ON/OFF and ZERO reference buttons) on the front face of the finder can be problematic. It can be cumbersome to reliably press these buttons and accurately set the ZERO reference point, particularly since the finder tends to slide along the work surface when a button on the front face of the finder is pressed.
Conventional digital angle finders commonly feature two varieties of inclination measurements. The user can choose to employ an absolute zero point and thereby obtain angular measurements relative to the center of the earth. Alternatively, the user can select and employ an incremental zero point that allows angular measurements to be taken relative to any arbitrary reference surface. Conventional finders permit the user to alternate between these two modes by engaging a button to switch the screen display to the desired mode. Switching between absolute and incremental measurements can be confusing and cause the user to record incorrect measurements.
However, if above mentioned digital angle finders are used for the corner of the wall, the angular measurements is hard to be relative to the center of the earth.